I am pretty new to QL but learning, a thought came about when I was fiddling with QL. After selecting powders, you can see on the chart where it says Propellant burnt %. My question is, is it best to select a powder when the propellant burnt % is less than 100 %? Reason I asked is because the bullet is still being pushed out the barrel and still under force until it exits the muzzle. If the propellant is 100% burnt by the time the bullet exits the muzzle, will it have an effect on accuracy since its "free flying" down the barrel without any force behind it?

Most often the powder that will burn has done so by the time the bullet has moved only a few inches. Just because the powder may be 100% consumed within six inches does not mean the gases are not still under very high pressure.

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Originally Posted By: Ronald Reagan

It's not that liberals are not smart, it's just that so much of what they know isn't so.

Big Stan, what caliber are we talking about, first? Selecting the right powder depends a lot on matching up the caliber and bullet you plan to shoot. Some calibers I shoot have a 95-99% burn. Some subsonics have a 75-80% burn. If you burn up all the powder used, then the round becomes more efficient in using all the powder that's available. But if you go to slower burning powder and heavier bullet, you may only get a 95% burn, but your velocity goes up, but the efficiency of doing so will go down. Kind of like an old 60's Camaro with a bigger carburetor getting more fuel into the engine and less mpg.

In the example below over half of the powder is burned before the bullet has traveled 2 inches and pressure is already dropping off. By the time the bullet has traveled 6 over 80% of the powder is burned. 90% burn by 9 inches. To see this in quickloads use the 8th button selection at the tip to display in tabular form.

About the slowest burn completion I've been able to cook up was around twelve inches in a very large cartridge with a very slow powder. In cartridges like .308 you'll usually see burn stop at around four inches or so.

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Originally Posted By: Ronald Reagan

It's not that liberals are not smart, it's just that so much of what they know isn't so.

With the example above but change powder to Varget and 90% burned by 5.75 inches with the other 10% burned over the next 13.6 inches or so of bullet travel.

You are correct, Kevin. I am a bit perplexed...this goes against what some highly regarded gun writers have said and which I always took as gospel. I haven't made much use of this function in QL, and after playing around with a few cartridges and powders I have seen some stuff that really surprised me. The few times I did check out the consumption curve, I saw confirmation of the "first few inches" dictum and never messed with it thereafter. After having played with it a bit this evening with a variety of cartridges, I can see I'm going to have to play with it a lot more to get a handle on some of the surprises I discovered.

The thing is, though, once a bullet has traveled down the bore 10 or 12 inches the pressure will have fallen to about half of the peak value, and the the volume of containment will have expanded several times making the additional gas provided by the burn of the last few percent of the charge almost, if not entirely inconsequential in terms of velocity.

It's actually a pretty interesting thing, and I'll be looking at some of the things I've seen that really surprised me.

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Originally Posted By: Ronald Reagan

It's not that liberals are not smart, it's just that so much of what they know isn't so.

Consultation with one of the "highly regarded authorities" has confirmed that the axiom stating that "all the powder that will burn does so in the first few inches ahead of the chamber" originated with Homer Powley. I knew I had stuck that factoid in my brain because it had come from a credible source, I just couldn't remember who the source was.

I wish I knew an easy way verify what QuickLOAD predicts, but I think about the best that can be done would be to see if it can predict when less than 100% burn is realized by decreasing charges and by shooting with a large sheet out in front of the muzzle. I have to wonder how Powley came to his conclusions also. Since I've not read his book I wouldn't even begin to guess.

I will restate what I think is important, though (assuming QL is right): by the time 95% of the powder has burned, the confinement volume for powder burn will have expanded to the point that the effect or influence of the burn of the last 5% of the charge will be greatly diminished.

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Originally Posted By: Ronald Reagan

It's not that liberals are not smart, it's just that so much of what they know isn't so.